Solder is a fusible metal alloy used to create a permanent bond between metal workpieces. The word ''solder'' comes from the Latin ''solidare'', meaning ''to make solid''. Soft solder typically has a melting point range of 90 to 450 deg C (190 to 840 deg F), and is commonly used in electronics and plumbing. Alloys that melt between 180 and 190 deg C (360 and 370 deg F) are most commonly used. Soldering performed using alloys with a melting point above 450 deg C (840 deg F) is called ''hard soldering'', or brazing.

The lead-free galvanizing solder formulation designed specifically for high-quality repairs to galvanized steel surfaces; composition of alloy is Tin-Zinc-Copper (Sn50Zn49Cu1) having melting point 200/300 (deg C). Other alloys are Tin-Copper-Silver (Sn95.5Cu4Ag0.5) with melting point 226/260 (deg C). Tin-Zinc-Copper (Sn90Zn7Cu3) is melting point 220/222 (deg C). Sn95.5Ag3.9Cu0.6 is low cost and has good bonding properties; used for fabrication of car radiators and fuel tanks, for coating and bonding of metals for moderate service temperatures.

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